The "Elsinore Project" Thread

[weltersys]

The cap has a reactance curve. Microphonics created by the AC current passing through the cap causes the reactance to change, depending on the construction and materials used (obviously mass and damping as well as no air gaps etc, these all come into play). As it is in series with the voice coil, then we have some kind AM, amplitude modulations, of the current. This ends up in the voice coil, and hence we hear it. Different caps will not all behave them same. Cause and effect would seem to exclude other explanations. What do you think?

Capacitive reactance is the variable resistance of a capacitor being controlled by the applied frequency.

Microphonics describes the phenomenon where a component transforms mechanical vibrations into an electrical signal, the reverse would make the capacitor make noise.

I think if either of those phenomenon have an audible effect in the output of a passive crossover, something is wrong with the circuit or components chosen for it


https://www.diyaudio.com/community/threads/capacitor-microphonics-question.384835/#post-6986865

Art

 

[Joe Rasmussen]

Thank you. It is what it does to the current via the voice coil in a magnetic gap, that is what must be important. Or else we shall hear nothing at all. But we do hear it. I propose that it it AM distortion of the current and that it causes the amplifier to produce this current. If others have a different view, then so be it.

 

[dmcgown]

Concerning capacitor noise, it is interesting that the most highly regarded capacitors (Duelund, Miflex, and even for that matter the Audyn True Copper Max) are potted withing a rigid fiberboard tube and use dense foil plates (copper, even silver for the Duelund). The construction is optimized against vibration. It makes me wonder if as a DIY effort potting less expensive but well regarded tape covered capacitors would have a significant benefit. That may be an experiment for me to try, I have some good sounding CDE 942 series hybrid film/foil caps I use for coupling in tube amps, and it would be nice to see if they can be improved cheaply.

Anyway, any verdict yet on the Miflex caps in the ULD tweeter crossover?

Thanks.

David